Shuttle program enters its heyday
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The shuttle Columbia lifts off for its first mission on April 12, 1981
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By Richard Stenger
CNN.com Writer
(CNN) -- The world's only reusable space vehicle has both soared
far above expectations and faltered with heartbreaking
consequences since first roaring into the sky 100 flights and 19
years ago.
While initially envisioned a fully reusable commercial space
plane, the shuttle that emerged in the 1980s was smaller than
expected and only semi-reusable.
NASA touted it as an economic and efficient means of
space transport, but whether it has succeeded remains a subject of
debate. Per unit of weight, shuttle payloads cost many times more
than those delivered by unmanned rockets.
But the shuttle delivered on NASA's promise to provide an
extremely versatile, reliable cargo ship that can be used over
and over again.
The workhorse has taken more than 600 passengers and 3 million
pounds of cargo into orbit. In cumulative spaceflight time, the
fleet has logged almost 2.5 years, its passengers nearly 15.
Shuttle crews have docked with two space stations, repaired the
Hubble Space Telescope three times, launched missions to study
planets and the sun and tested the effects of weightlessness on
industrial materials, leafy plants, mice and humans.
NASA historian Roger Launius has called the shuttle "the cornerstone of the U.S. space program" and a driving force behind NASA budgets for decades.
Euphoria and tragedy
Since Columbia lifted off on April 12, 1981, the shuttle has experienced
numerous milestones during its service, some agonizing and others exhilarating. Among the most memorable moments:
• After Challenger completed nine missions, the shuttle and its crew were lost
in an explosion 76 seconds after launch on January 28, 1986.
Following extensive safety upgrades on the fleet, the shuttles returned to service with the flight of Discovery on September 29, 1988.
• The youngest shuttle, Endeavour, lifted off for its maiden voyage on March 24, 1992. Following the Challenger accident, NASA used parts set aside to repair damaged orbiters to build it.
• Endeavour returned to the Hubble Space Telescope in early December 1993 so astronauts could correct a debilitating flaw in the main mirror of the orbiting observatory.
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The space shuttle Challenger breaks apart moments after the explosion on January 28, 1986
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• A shuttle Atlantis mission that began June 27, 1995, marked the 100th U.S. manned flight in space and the first shuttle docking with the Russian Mir space station.
• Another milestone took place on October 29, 1998, when John
Glenn, the first American in orbit, returned to space aboard
Discovery.
• Endeavour embarked on the first assembly flight to the orbiting
International Space Station on December 3, 1998. The crew
attached the U.S. segment Unity to the Russian module Zarya.
• Columbia narrowly averted disaster on July 23, 1999, when a
short-circuit six seconds after launch shut down critical engine control computers. The mission continued, but NASA grounded the fleet for
an exhaustive wiring inspection.
Ever-evolving fleet
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Charles Precourt, chief of the Astronaut office in Houston, and Daniel Goldin, NASA administrator, welcome Sen. John Glenn back to earth after his return to space in 1998
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The shuttle fleet has evolved constantly over its nearly 20-year history. Lighter fuel tanks have increased cargo capacity by more than 8 tons. Engine redesigns have dramatically cut launch risks more than 80 percent, according to NASA.
To improve safety and performance, NASA has installed a variety of other features, including a crew escape system, a drag parachute for landing, even a better toilet that allows longer missions.
NASA has spent four years and about $1 billion to develop a replacement for the shuttle. But the X-33 program has been plagued by serious design glitches. A half-built prototype faces daunting technological obstacles, and some engineering experts wonder if it will ever fly.
Because of the delays, NASA expects to rely on the shuttle for at least another decade. The space agency is confident the proven workhorse can do the job. Each of the four orbiters now in operation -- Columbia, Discovery, Atlantis and Endeavour -- is designed to fly at least 100 missions. The fleet still has more than three-quarters of its expected lifetime ahead.
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Artist's concept of the X-33, the proposed replacement for the shuttle
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Moreover, NASA predicts a major overhaul of the fleet over the next five years will cut the risk of launch accidents in half. Upgrades in the works include engine sensors that can detect potential trouble before it happens, engine nozzles that eliminate welds and "smart glass cockpits" that simplify flying tasks. Some of the shuttles already have been equipped with the new technologies.
Though nearly 20 years old, the shuttle fleet is only just now beginning to fulfill one of its original prime objectives: flying to a U.S.-led space station. The agency is calling on the shuttles to lift off seven or eight times annually for the next several years, mostly to expand and maintain the growing International Space Station. The flight schedule will be the busiest in shuttle history.
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Amazing facts about the space shuttle:
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• The most complex machine ever built, the space shuttle has more than 2.5 million parts, including almost 370 kilometers (230 miles) of wire, more than 1,060 plumbing valves and connections, over 1,440 circuit breakers, and more than 27,000 insulating tiles and thermal blankets.
• In 8.5 minutes after launch, the shuttle accelerates from zero to about nine times as fast as a rifle bullet, or 28,000 km/hour (17,400 mph), to attain Earth orbit.
• The space shuttle weighs more than 2.04 million kilograms (4.5 million pounds) at launch - over 1.59 million kilograms (3.5 million pounds) of propellants are entirely consumed in the next 8.5 minutes.
• If the shuttle's main engines pumped water instead of fuel, they would drain an average-sized swimming pool every 25 seconds.
• Because liquid hydrogen and liquid oxygen fuel the main engines, the majority of exhaust produced is water vapor.
• At launch, the shuttle's two solid rockets consume more than 9.07 metric tons (10 tons) of fuel each second and produce 44 million horsepower, equal to 14,700 locomotives.
• The three shuttle main engines produce power equivalent to 23 times that produced by the Hoover Dam.
• The shuttle's solid rockets burn powdered aluminum as fuel -- a different form of the same type of material that is used as a foil wrap in most kitchens.
• The temperatures inside the shuttle's main engines and solid rockets reach more than 3,315.6 degrees Celsius (6,000 degrees Fahrenheit), higher than the boiling point of iron, yet the main engine's fuel -- liquid hydrogen -- is the second-coldest liquid on Earth at minus 252.8 degrees Celsius (423 degrees Fahrenheit).
• The discharge pressure of a shuttle main engine turbopump could send a column of liquid hydrogen 57.9 kilometers (36 miles) into the air.
• Temperatures experienced by the shuttle range from as low as minus 156.7 degrees Celsius (minus 250 degrees Fahrenheit) in space to as high as 1,648 degrees Celsius (3,000 degrees Fahrenheit) as it re-enters the atmosphere.
Source: NASA
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RELATED SITES:
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